1. Field of the Invention
The present invention relates to an integrated active pixel photosensor including a matrix array of pixels, each pixel including a photosensitive component, an amplifier component and a reset to initial state component, and the matrix array further including, for controlling the pixels, an addressing device, a power supply device, a reset to initial state device and a device for reading luminance information picked up by the pixels to extract the information from the matrix array.
2. Description of the Prior Art
In this kind of photosensor only part of the total surface area of the chip on which it is implemented is sensitive to light, the remainder of the surface being occupied by components and conductors. This is why the xe2x80x9cfilling factorxe2x80x9d of these arrays is relatively low.
In one prior art photosensor each pixel comprises three active components, such as transistors, respectively implementing the functions of amplification, addressing and resetting to the initial state (hereinafter RIS). The matrix array requires four types of conductor connected to the cells for implementing the functions of power supply, information output, read control and RIS control. If the photosensor uses the 1 xcexcm CMOS technology, a pixel of the array will have a filling factor of only 40% and a surface area of 15xc3x9715 xcexcm2.
The proposal of Hisanori Ihara et al. submitted to the IEEE International Conference on Solid State Circuits, 1998, session 11, document FA 11.8, relates to a matrix photosensor array pixel comprising only two transistors, one for amplification and the other for RIS, but the pixel further includes an addressing capacitor specially integrated on the chip alongside the active components.
The addressing capacitor is a disadvantage which, compared to the prior art briefly referred to above, further penalizes the filling factor, as it requires additional surface area. Also, the RIS select line of the circuit must carry very similar analog potentials (typically 0.9 V and 2.1 V) during the respective phases of integration (acquisition of the luminance signal) and pixel reading. It is difficult to fix these close potentials, especially as this must be done in a very short time period.
An object of the invention is to provide an integrated photosensor of the type defined above which is free of the disadvantages of the prior art discussed above.
The invention therefore provides an integrated active pixel photosensor including a matrix array of pixels, each pixel including a photosensitive component, an amplifier component and a reset to initial state component, and the matrix array further including, for controlling the pixels, an addressing device, a power supply device, a reset to initial state device and a device for reading luminance information picked up by the pixels to extract the information from the matrix array, in which photosensor the addressing, power supply, reset and reading devices are implemented by the same plurality of matrix array column and row lines and the photosensor further includes logic control devices external to the matrix array and connected to the column and row lines to enable selective control in each pixel of the power supply, addressing, return to initial state and read functions.
Accordingly, each pixel of the matrix array can be implemented using only two active components, and it is not necessary to use any specially integrated capacitor. Also, the circuit in accordance with the invention requires a very small number of connecting lines. The filling factor of the matrix array can therefore be significantly greater than in the prior art.
Other features and advantages of the present invention will become apparent in the course of the following description, which is given by way of example only and with reference to the accompanying drawings.